These results, which evaluated samples from 2,137 patients, suggest that the PAM50-based Prosigna breast cancer prognostic gene signature assay may help identify women with late distant recurrence after five years of endocrine treatment.

Using the Prosigna assay, the study investigators classified patient tumors by subtype and found that patients with Luminal B subtype have three times higher risk of late distant recurrence than patients with Luminal A subtype tumors.

Results were presented at the 2013 San Antonio Breast Cancer Symposium.

Authors of the study reported that the ROR score, also known as the Prosigna Score, added prognostic information about the risk of ten-year distant recurrence beyond that provided by standard clinical-pathological variables in the analysis of all patients studied.

In addition, the study reported that patients with Luminal A subtype (4.1%) had a lower risk of recurrence than those with the Luminal B subtype (12.9%) further supporting the biological differences between these groups.

NanoString Technologies president and CEO Brad Gray noted few studies have addressed the prognostic value of molecular scores for late recurrence.

"These results add to the growing body of data supporting the clinical potential of the PAM50 gene signature and the Prosigna Breast Cancer Assay as a valuable prognostic tool for patients and their doctors," Gray added.

Results presented at the 2013 San Antonio Breast Cancer Symposium build on a recently published paper in the Journal of the National Cancer Institute titled, ‘Factors predicting late recurrence for estrogen receptor positive breast cancer’.

Authors of this paper found that the PAM50 gene signature was better than Oncotype DX and IHC4 Assays at categorizing patients into low and high risk for late distant recurrence of disease.